Effects of low concentrations of enflurane on probability learning.

The effects of controlled subanaesthetic concentrations of enflurane on learning behaviour and on ability to change previously developed decision strategies were studied in 10 male volunteers, using a probability learning task. Subjects were instructed to predict on each of 200 consecutive trials, whether a left or a right light would appear. The appearance of lights was pre-determined by a set relative frequency unknown to the subject. The relative frequency was automatically changed at the end of the first 100 trials, from 8/10 lights in the left side to 4/10. It was found that enflurane at subanaesthetic concentration of 0.25% (end-tidal) slowed the rate of learning, and increased the number of trials required for readjusting the prediction strategy to the changed situation.